Wildlife Spotlight: Texas Diamondback Terrapins (Malaclemys terrapin littoralis)

Diamondback terrapins are an elusive and rarely seen coastal species, once on the brink of extinction.

Many years ago I had to help write a big report for my job, as I often do, and part of that report was analyzing impacts to certain wildlife species. One of those species for that report happened to be Texas diamondback terrapins. This project was, broadly speaking, within the Galveston Bay region, and so as I was compiling information and reading about the species to summarize for the report, I thought I would likely never happen to see a diamondback terrapin for myself in the wild.

Part of this reason is that while I live within an easy driving distance from Galveston Bay and the Gulf of Mexico, I’m not down there very frequently. And when I am down there, I’m not paddling or boating in the parts of the bay they are likely to occur. My husband ended up seeing some on a remote beach in western Louisiana in 2014 but it wasn’t until October 2021 that I saw one for myself.

You may be asking, what is a terrapin? How does it differ from a turtle or tortoise? Diamondback terrapins are turtles, in the Family Emydidae, alongside pond and box turtles. Diamondback terrapins belong to the genus Malaclemys and thus all terrapins in the US refer to this genus. You may find yourself in the UK at some point and they will lump all freshwater turtle species into the terrapin lingo, so be cautious over there to know they aren’t referring to just this particular species.

Diamondback terrapins are from one species, Malaclemys terrapin, but form 7 subspecies ranging from the Texas coast all the way up to New England. Those are:

• Carolina Diamondback Terrapin Malaclemys terrapin ssp. centrata

• Texas Diamondback Terrapin Malaclemys terrapin ssp. littoralis

• Ornate Diamondback Terrapin Malaclemys terrapin ssp. macrospilota

• Mississippi Diamondback Terrapin Malaclemys terrapin ssp. pileata

• Mangrove Diamondback Terrapin Malaclemys terrapin ssp. rhizophorarum

• Florida East Coast Terrapin Malaclemys terrapin ssp. tequesta

• Northern Diamondback Terrapin Malaclemys terrapin ssp. terrapin

The northern diamondback terrapin is by far the most common subspecies sighted on iNaturalist.

As I’ve mentioned, diamondback terrapins are coastal, brackish water species, found throughout estuaries on the Gulf and Atlantic coasts of the US. Along with their sea turtle compatriots, they were a target of the turtle fisheries in the late 1800s and throughout the first half of the 1900s, and thus their populations suffered greatly. Eventually laws were enacted to stop the decimation of our coastal and oceanic turtle populations but terrapins today still face issues that can result in their demise and destabilize their populations. Becoming trapped in crab traps, fishing line, or loss of habitat are all major actions threatening the lives of terrapins today. Roads are also dangerous for disoriented terrapins as is beach driving for nesting terrapins.

Despite all of this, the species and its subspecies are not listed federally as endangered or threatened, and though I saw several reports referencing that the Texas diamondback terrapin is state listed, it isn’t showing up on the Texas Administrative Code threatened or endangered lists. I do see with Texas Parks and Wildlife county lists they are considered an S2 species, which means Imperiled, and they are considered a Species of Great Conservation Need (SGCN).

In the estuaries they are found, they can be seen feeding on crabs, shrimp, bivalves, fish, and insects, then burying themselves in mud at night or covering themselves even further in the mud to hibernate during winter months. And just like sea turtles, the sand temperature affects the outcome on sex for the eggs—the cooler temperatures produce males while the higher temperatures produce females.

So, how did I finally manage to see Texas diamondback terrapins? It was all thanks to the folks at Goose Island State Park who posted on their Facebook page in 2021 that the public could view the terrapins from the boat ramp at the state park. And sure enough, we found them! I normally would not share locations for species such as this due to its highly sensitive nature and, I hate to say this, but you can’t trust people because they poach and kill. I’ve seen orchids ripped off trees in south Florida—I don’t tell people where orchids are unless I know them personally, and even then…people tend to tell one person and then you lose track of who knows and then you have orchids ripped off trees the next time you go out to the swamp. However, this is within a state park, the state park mentioned it on a public page, and if you get caught poaching in a state park, well good luck with that!

Also, everyone deserves to see wildlife up close, too. Siloing access to hard to see and rare species is done for a reason, to protect that species from the humans that mean to cause it harm. But at the end of the day, it is beneficial to provide access to some of these populations, whether plant or animal, so people know they even exist and that they matter. It’s one thing seeing an animal in a zoo but a complete other to see it exist in the wild. Most of us will never see much of the wildlife we know to be in peril on this planet but if we have the opportunity to educate and provide some access to future generations for some of them in our own backyards, I believe it goes a long way in cultivating a sense of empathy and care about our ecosystems.

Overall range for diamondback terrapins, Malaclemys terrapin.

This is a map from iNaturalist of the overall range for diamondback terrapins. I had to check out what was going on in Bermuda, figuring it was an introduced population. Turns out it isn’t—it’s a population that likely found its way there on the Gulf Stream between 400-3,000 years ago! They seem to be more closely related to the Carolina subspecies. You’ll also notice the random points in California and Oregon—those appear to be released pets found in local ponds. There were a couple over in Hawaii too but I cut that out of the screenshot.

Texas diamondback terrapin range

iNaturalist will give you a good idea of overall range here in Texas but all actual locations are obscured. If you find yourself paddling or boating in any of these estuaries, keep your eye out for this amazing species!

My only encounter on the Upper Texas Coast last summer on Texas Point NWR, very near the jetties at Sabine Pass. They are out there…

Further Reading:

• Identifying Diamondback Terrapin Nesting Habitat in Mission-Aransas Estuary, Texas

• Population Survey of the Texas Diamondback Terrapin in San Antonio Bay, Matagorda Bay, and Sabine Lake

• Spotlight on a Species: Diamondback Terrapin

• TPWD Texas Diamondback Terrapin

Misti writes regularly at Oceanic Wilderness and can be found on Instagram at @oceanicwilderness. She hosts two podcasts, Orange Blaze: A Florida Trail Podcast, and The Garden Path Podcast.